Method of producing a pulling stress and hydraulic pulling mechanism



Nov. 30, 1937. s. MANDL ET AL 64 METHOD OF PRODUCING A PULLING STRESSAND HYDRAULIC PULLING MECHANISM Filed Margh 16, 1935 3 Sheets-Sheet 1Nov. 30, 1937. s. MANDL ET AL METHOD OF PRODUCING A PULLING STRESS ANDHYDRAULIC FULLING MECHANISM Filed March 16, 1955' 5 Sheets-Sheet 2 EcZzz/afd M Hausa?" Nov. 30, 1937. s. MANDL ET AL 2,100,564

METHOD OF PRODUCING A PULLING STRESS AND HYDRAULIC PULLING MECHANISMFiled March 16, 1955 3 Sheets-Sheet 3 JQz/en Z'orv ziegmund/wandl, Ewan1P awe)".

Patented Nov. 30, 1937 PATENT OFFICE IiIETHOD 0F PRODUCING A PULLINGSTRESS AND HYDRAULIC PULLING MECHANISM Siegmund Mandi and Edward M.Pfauser, Milwaukee, Wis., assignors to Blackhawk Mfg. 00., Milwaukee,Wis., a corporation of Wisconsin Application March 16, 1935, Serial No.11,514

24 Claims.

This invention relates to hydraulic pulling mechanisms, and moreparticularly is directed to. a pulling mechanism whereby hydraulic forceis applied in controlled quantities to displace or deform metal framemembers, specifically for bending and straightening such members.

Heretofore, the application of hydraulic pressure for such operationshas been extremely difficult, due to the impracticability of position-'ing the hydraulic pressure-applying unit in a location suchthat thefull effective force developed by the unit can be utilized for thepulling operation. Bending and twisting stresses incident to thedevelopment of a hydraulic pressure in devices heretofore employed havebeen transmitted directly to the unit, tending to make its positioningboth precarious and dangerous to the operator. 'Further, in operationsof this type, spacial limitations prevent the proper use ofhydraulicjack units of the type now employed in garages, repair shops and similarestablishments.

We have found that in order to securethe most advantageous applicationof hydraulic pressure it is distinctly desirable to dissociate thepressure applying or pulling mechanism from the source of pressuresupply, or pump unit. This feature has been brought out in suitabledetail in the copending application of Edward M. Pfauser, Serial No.4,728, filed February 4, 1935, in which the provision of a metalstraightening machine including a power unit of general utility for theapplication of hydraulic force to the straightening disclosed.

The present invention contemplates the provision of 'a pulling mechanismwherein the entire available hydraulic pressure may be utilized for thepulling operation, and no portion of this force need be dissipated inmaintaining the mechanism in position, or in absorbing and overcomingthe bending and twisting stresses developed at the pump unit. Infurtherance of this concept, we provide'a pulling mechanism or bendingof metal members is to our knowledge, heretofore been incorporated. in amechanism employing a portable ram or power unit dissociated from thepressure supply or pump unit. In the present invention, the ram unitcomprises a pressure cylinder and an axially reciprocating plungermounted therein and movable in'response to fluid pressure manually de--veloped and controlled by a pump unit disposed at a remote point, thepressure being transmitted to the power unit through a flexible'conduitthat prevents the transmission of stresses from the pressure developingunit to the power applying unit. As disclosed fully in the Pfauserapplication aforesaid, the ram unit is operable in any desired angularposition and is thus all-directional in use.

Further, the particular manner of connecting the power unit foroperation provided by the present invention possesses certain distinctadvantages not heretofore obtainable. The mechanism is capable ofalining itself automatically into operative position, and permits thepulling force to be. exerted in a direction such that maximum pullingeffect per unit of force applied is produced.

Another feature of our invention, which is of distinct advantage, is theprovision of adjustable coupling means whereby the'machanism is capableof adjustment in accordance with the spacing between the two membersbetween which relative movement is to be effected, in order toaccommodate the mechanism to various spacing between such members. Inaddition, we preferably provide a link or chain connection of themechanism to the members, so that the pulling effort is exerted throughnon-rigid means, and thus the direction of pull is preferably at alltimes along a line extending substantially normal to the plane of themember being pul1ed, which is distinctly advantageous in applying forcefor this purpose.

In order to provide meansforrapid and simplified connection of thepulling mechanism in operative position, we provide, in the presentinvention, a novel type of chain-pull plate, one of the plates beingpreferably secured to the base or fixed end of the power unit, while thesecond plate, of similar design, is secured to the projecting end of thepower plunger. Thus, upon extension of the plunger due to theapplication of hydraulic pressure to the power unit, the plates aremoved away from each other, providing a commensurate pulling forcebetween the members about which the chains have been s cured i We havefound that in straightening of metal members frequent sighting ormeasurement of the deflection of the members is desirable, in order tosecure accurate bending or straightening thereof. By the provision of agraduated plunger in the power unit, we are able to secure a positiveindication of the deflection of the member being bent or straightened,and can thus determine to a quite accurate degree the exact amount ofpressure which is applicable for predetermined displacement of themetal. This allows the operator to judge the deflection of the memberwithout the necessity of auxiliary sighting apparatus, and preventsoverstressing of the metal, or bending of the member to an extent,greater than that desired.

The present invention is of relatively simple mechanical design,employing a small number of parts, and is capable of rapid connectioninto and disconnection from its operating position, whereby its use ingarages, repair shops and similar establishments is of .distinctpractical advantage.

Other objects and advantages secured by the present invention will bedescribed in detail in connection with the following specification,

, which, taken in connection with the accompanying drawings, willdisclose to those skilled in the art the particular construction andoperation of a preferred form of our invention.

In the drawings:

Figure 1 is a perspective view of the pulling ly on line 5--5 of Figure4, showing in detail the construction of the pull plates;

Figure 6 is a perspective view showing a somewhat modified pullingmechanism embodying the present invention;

Figure 7 is a top plan view of one of the chainpull plates shown inFigure 6; and

Figure 8 is a sectional view taken on line 8-8 of Figure 7.

Referring now in detail to the drawings, in Figure 1 we have disclosedthe application of our hydraulic pulling mechanism to the straighteningof a front axle assembly of an automotive vehicle.

The front axle is indicated at 5, and is provided with rearwardlyextending radius rods 6 forming a substantially V-shaped structure. The

axle 5, in this embodiment of the invention is shown as being bentoutwardly, and the mechanism which we have provided is for the purposeof pulling the axle 5 inwardly toward the joined ends of the radius rods8.

The pulling unit, as shown more particularly in Figure 2, comprises ahydraulic ram unit 1 having a base portion 8 and an axially extensibleplunger 9, the ram unit being of the type described in detail in theabove-identified copending application of Edward M. Pfauser.

.The base 8 of the ram I is provided with a threaded recess adapted toreceive a coupling member l0 threaded thereinto, and having bearingengagement within a pressure plate l2 secured thereto. A pair of yokerods l3 are secured at one. end in suitable opposed openings in theplate l2, and are prevented from axial displacement out of theseopenings by means of nuts l4 threaded onto the ends of the rods.

The plunger 9 of the ram unit has a threaded head portion l5 extendinginto a suitable pull plate l6 having opposed openings receiving the rodsl3, the pull plate l6 being adapted for sliding movement longitudinallyof -the rods.

The rods l3 are extended outwardly of the pull plate I6 for any desireddistance, and adjacent their outer projecting ends are provided with asecond pull plate ll, of the same general form as the pull plate 16,which is mounted for movement on the rods I 3 by means of opposedopenings formed therein, the plate I! being prevented from displacementoutwardly of the rods by means of a pair of nut members l8 threaded ontothe projecting ends of the rods.

The ram unit I comprises a ram cylinder flexible fluid pressuretransmitting conduit 28 coupled as at 22 to the base 8 of the ram unit.This coupling provides communication between the hose 2!! and theinterior of the ram cylinder. The flexible conduit 20 at its oppositeend, is coupled to the outlet port 23 of a pump unit 24,

the pump unit 24 being of the type disclosed in detafl in theabove-mentioned copending application of Edward M. Pfauser.

The pump member comprises a pump cylinder or reservoir containing thefluid to be placed under pressure, and a rocking beam 25 adapted to berocked about pivot 26 by means of an actuating lever 2'! to producereciprocation of the pressure plunger within the head end 28 of the pumpunit, thereby drawing fluid from the reservoir of the pump unit andtransmitting it under pressure to the conduit 20 through the outletport- 23. The pump unit 24 is provided with a laterally projecting footportion 29 at its forward end, adapted to be engaged by the foot of anoperator, and a clamping member 30 at its rearward end having anupwardly disposed foot portion 32 adapted to be engaged by the oppositefoot of the operator, whereby the pump unitmay be mam adapted to receivefluid under pressure from a tained in flxed position on thefloor duringreciprocation of the operating handle 21.

The present invention is not concerned primarily with the details of thepump construction, and reference may be made to the above-mentionedcopending application for a fuller explanation of the operation thereof.

The ram unit I, as shown in Figure 1, is disposed within the triangularstructure formed by the axle 5 and the radius rods 6, and the plate I6is provided with opposed chain latching portions adapted to receive theopposite ends 34 and 35 of a chain member which, at its intermediateportion, is wrapped around the juncture36 of the radius rods. The ends34 and 35 of the chain may be adjustably'secured in fixed lockedposition upon the plate I6, whereby actuation of the plunger 9 due to'fluid pressure within the ram cylinder results in movement of the platel6 outwardly along the rods l3, thereby placing tension upon the chainbetween its fixed clamped ends 34 and 35 and theportions 36 thereof.

Similarly, the plate member I! is. provided with chain gripping portions31, receiving the ends 38 and 39 of a second chain member 40, wrapped Itis apparent, therefore, that upon reclprocation of the actuating handle21 ofthe pump unit the left, as shown by' the arrow in' Figure 2. Thisresults in the plates l6 and I1 having relative movement towardeachother when pressure is applied "to theiram' -unit, which results inshortening the distance between the portions 36 and 42 of thechains',and producing a pulling tension uponthe axle 5 tending toibend'and/fstraighten the same;

The plunger 9' is preferably provided with' graduated indicationsfasshown in Figure 2, and the operator, standing at the pump unit 24, can

actuate th e pump-21 and thus control the amount of pressure transmittedto the unit 1. At the" same time, by noting theggraduations on theplunger 9, anypredetermined defiection of the;

axle or other membefj5fcanbe produced. Thus, if the operator hasascertained'that'a sponding movement of the plunger 9, indicated by thegraduations thereor'i, whereby the deflection of the" member 5 maybeaccurately con-" trolled. Further, itfis'to be notedthat the de--velopment of pressure at the pump unit 24, which produces stresses atthe pump unit, will not act to transmit these stressesto the ram unit 1,inasmuch as the flexibleconduit is interposed therebetween. [Thisconduit 20 is pre'ferably' formed of a suitable metal reenforced cableprovided with a rubber or other resilient body por-' tion.

Referring now to the structure shown in' Figure 3, the ram unit 1 ofthis embodiment of the invention has its base 8 provided with a suitablecoupling member to which a chain pull plate 48 is directly secured. Atits opposite end, the ram plunger 9 is threaded into a depending socketportion 50 of a second chain pull plate 52 shown in detail in Figures 4and 5. The two plates 48 and 52 are substantially ident cal in design,and correspond to plates l6 and H of the embodiment shown in Figure 1.

Considering now Figures 4 and 5 in detail, the

pull plate 52 is provided with a plurality of radially extending tongueportions. one pair of tongue portions 53 being provided with openings 54adapted to provide guiding means for chain members, such as the chainmembers 55 and 55 of Figure 3, therethrough.

Extending at right angles to' the opposed tongues 53 are a pair of dametrically opposed lug members 51, which members are provided. at

their ends, with inturned spaced edges 58 defining slots 59 extendingradially inwardly toward the center of the plate. Suitable web portions60 are formed centrally of the members 51, and extend to the definingedges of the slot 59, forming recessed slotted sockets adapted to"secure chain links therein. As shown in Figure 3, a link member isadapted to slide laterally into the slot 59, and the adjacent linkmembers then have abutting engagement against the web portions 60 forlimiting movement of the chain member with respect to the plate.

The plate 52 is internally threaded within the V 9.5m" chain 40, wherebythe plate jl1;tends-to-move to cylindrical opening 53.

socket projection 50 to receive the threaded end 15 of the ram plunger9, and above this portion is an annular recess 62 forming a slightclearance for threading of the ram plunger 9 into and out of the plate.Above the recess 62 the plate .52 is provided with a central cylindricalbore 63 extending to the outer surface of the other side of the plate,and providing a socket for receiving a drift pin 64 or the like,employed for punching or pressing out wrist pins, bearings andthe like.A suitable threaded radially extending opening 65 is provided betweentwo of the extending leg portions of the plate 52, and extends into theThe opening 65 is adapted to receive a suitable set screw 66 which isthreaded thereinto to have bearing engagement against the surface of apin such" as the pin 64, to secure .and hold-ithe pin in'fixed positionwithrespect to the plate, preventing its displacement from the platewhen the plate is. reversed in posi-lv tio'n.

In the production of pulling .force between two i members, such as themembers 12 and =15 "of-' Figure 3, which maybe-spaced members adaptedf'to be pulled together, or"may comprise a fixed e c't o of two inchesof the center of 'the'axle 5 an-'r'espect to its formerpositionisdesirablejhe ma actuate the pump unit 24 to" producea corresupportingmember and a second member which is to be bent or straightened, orpulled toward the tween the members 12 and 13, and the plates 48 and 52are secured to the base 8 of the unit and to the plunger 9 thereof;respectively. The chains 55 and56 arev then secured inthe positionshown, the chain 55 being wrapped about, the member 13, having .its endsguided for movement in the 1 openings 54 of the plate 48, and thenextending along the ram unit on opposite sides thereof and being lockedin .fixed position within the slots 59 of the plate 52. The chain .56,on the other hand, has its intermediate portion wrapped around themember 12, and the ends thereof are extended i-hriough the guideopenings 54 oil the plate 52, and are locked in fixed position in theslots 59 of the plate 48. Upon the application of pressure to theinterior of the ram cylinder, the plunger 9 is moved axially outwardlyof the cylinder, tend-' "ing to move the plates 48 and 52 apart. Sincethe overlapping ends of the opposite chains are secured to these plates,this produces a tension stress upon each of the chains, tending eitherto draw members 12 and 13 toward each other, or to draw either one ofthese members towards the other, if the other member is a fixed support.

It will be noted that there is no structure which prevents theindependent movement of the ram unit 1 when connected in thismanner, andit is therefore apparent that upon the initial application of pressureto the unit, the unit will assume a position such that its axis lies ina line corresponding to the direction of pull between the members 12 and13, whereby a straight line tension pull is exerted between thesemembers. This is of material advantage in providing for maximum exertionof pulling force by the unit in accordance with the pressure appliedthereto.

Inasmuch as the slots 59 of the-two pull plates are adapted to receiveany of the links of the chain members, these chain, members may bereadily adjusted to the desired lengths necessary for proper spacing ofthe ram unit 1 betweenthe thereby elongating the ram unit 1, if thespacing .of the members 12 and 131s such as to require such extension.However, ordinarily the lengths of the chains can be varied sumcientlytoprovide for operation of theramunit within any desirew spacing ofmembers to be bent or straightened.

Referring now in rnore detail to' the'structure shown in Figures 6, '7and- 8; the ram unit"! is pm: vided, at its base 8, with a chain" pullplate-'18,

which is shown in more detailinFigures 7 and 8. The chain pull plate 18has a projecting cylindrical portion 12, internally threaded as at 13provided with oppositely extending arm portions 14 and I5, which armportions have guide openings 18 extending therethrough, the openings 18being for the purpose of providing guiding passages for the chainmembers which secure the ram in pulling position. Projecting upwardly ina direction opposite to the cylindrical portion 12. of the pull plate 18is aiboss 11, which boss defines an opening 18 out of the plane of armsI4 and I5 and extending in a direction normal to the axis of theopenings 18.

In the operation of the mechanism shown in Figure 6, one of the pullplates 18 is secured to the base 8 of the ram unit I by means of acoupling member or the like, while the other pull plate T8 is secured tothe threaded head of the axially movable plunger 8 carried by the ramunit. A chain member 19 has the intermediate portion thereof extendingthrough the opening.

18 of the pull plate 18 carried by the plunger, as shown at 88, and thetwo-extending ends of the chain member 19 pass throughthe guide openings16 of the pull plate connected to the base of the ram unit,one end ofthe chain being provided with a hook member 82 adapted to engage in andsecure any suitable link of the opposite end 83 of the chain [9, wherebythe chain may be adjustably hooked about any suitable member'to be bentor straightened, suchas the member 84. By the provision of the hook 82,it is apparent that the chain 18 may be carried by the ram unit, as theram'unit is moved into various positions, and all that is required toconnect it to the member to be operated upon is to hook the hook 82 inthe desired link of the end 83 of the chain 18, whereby the ram unit isadjustably secured in proper position with respect to the member 84.

Similarly, a corresponding chain member 85 has the intermediate portion86 thereof passing through the opening 18 in the pull plate 18 carsothat it may be hooked about a support in the same manner in which the.chain I9 is secured, if desired. By merely unhooking the hooks 82 and98, the ram unit, together with the .chains, maybe placed in any desiredpositionQthe chains being engaged in the bosses l1 and threaded throughthe openlngs'l6 so that a minimum of time is required for connecting theunit in position.- .1 5;

'The operation of the. mechanism showrliin Figurer6 is similar to thatdescribeddmconnection,

withFigure 3, the application 5! pressure through the conduit 28 to theram unit 1 causingextension of the plunger 9, which. in turn produces atension pull upon the chain 19, andacorrespond ing thrust against thebase of the ram unit, producing a tension pull upon-the chain 85. Asaresult, the plates 18 tend-tomove away from each other, and thus tend todraw; the secured ends 82, 83 of the chain 19 andgthe ends 81, 88 of rthe chain 'toward each other, thereby producing a pulling stress uponthe members 84 and-89, which pulling stress can be regulated asdesiredby the operator, by means of theindications produced by the graduationson the annular surface of the plunger 8, and the pressure-being appliedto the unit through the conduit 20.

It is therefore believed apparent that we have provided a ram pullingmechanism capable of producing a bending or straightening of any desiredmetal members with the maximum amount of force per unit of pressureapplied to the and in which the pulling force islexerted in a linesubstantially in the directionof desired pull.

The unit is capable of rapid adjustment and connectionbetween variouslyspaced, members, facilitating its use for a large number of operations,

could be employed for pushing the membersj'i2 and I3 apart, if suchoperation were desired. i,

While we have'disclosed the ram unit as particularly applied for pullingmechanism, therefore, we do not intend to be limited to theexactoperation and connection of the members asshown and described, but only,in so far as vdefined by the scope and spirit of the appended claims. I

Weclaim: r. v

1. In a mechanism of the class described com: prising a power unitincluding an axially movable plunger, separate means carriedbytsaidplunger and at the opposite end of said unit for receiving separatechain members,-each of said means in, cluding means for guidingthemovement .of,;the chain member, secured to .the.-ot l 1er,o f,saidmeans, and a flexible conduit connectedtolsaidjunitlfor supplying liquidunder pressurathereto'to. move, said plunger outwardlypf said jufniti,

2. In a -mechanism,of'the,class'described, a power unit, chain-pullplates at opposite ends of said .unit chain-fmembers having their inter:

mediate portion's'looped about. spaced metal members and having. theextending ends thereof secured to said plates, and means for applyinghydraulic pressure to said unit for moving said plates away from each'other to produce a tension stress upon said chain lmembers between saidspaced metal members.

3. In a mechanism of theclass described, a portable ram unit, pullplates at opposite ends thereof having laterally spaced latchingportions, separate flexible tension members each secured to the latchingportions oi the pull-plate at one end of said unit and extendingalongside and then outwardly beyond theiopposite end of said a bers, andmeans for expanding said unit axially to move the secured ends of saidtension members away from each other whereby a tension stress isproduced between said metal members.

4. In a mechanism of the class described for producing a tension stressbetween two spaced members, a portable ram unit capable of being placedbetween-said members, chains connected to each end of said unit andextending outwardly of the opposite ends of said unit for connection tosaid members, and means at said opposite ends of said unit for guidingthe extending portions of said chains whereby uponaxial extension ofsaid ram unit said chains automatically aline' said unit in thedirection of the tension stress between said spaced members.

5. In combination, a power unit comprising a ram cylinder and a ramplunger movable axially outwardly of said cylinder, chain plates on saidplunger and said cylinder, chains carried by each of said plates andpassing through the other of said plates ,for connection to a pair ofspaced members, and means for transmitting hydraulic pressure to saidcylinder to expand said power unit axially whereby said' chains exert apulling stress between said spaced members.

6. A chain-pull plate for a pulling mechanism of the class describedhaving a central threaded guiding means in the recess, a pair ofopposite disposed guide means spaced from said recess, and a pair ofchain-engaging lug portions disposed on opposite sides of said recessand extending normally to'said guide means. i

'7. A chain-pullplate for a pulling mechanism of the class describedcomprising a plate member of generally cruciform shape, a threadedrecess formed centrally in said plate member for attaching said memberto a power unit, a pair of chain-engaging lug means formed in one pairof oppositely projecting'arms of said member, the other pair ofoppositely projecting arms having guide'means formed therein capable ofslidably receiving chain members.

8. A chain-pull plate for a pulling mechanism of the class describedcomprisinga central portion having an internally threaded recesstherein, four arm portions projecting radially outwardly of saidcentralportion,chain-engaging lug meansin two'of said arm portions, andchain other two of saidarm portions. F

9. In a mechanism of the class described, a power unit, a pump unit fordeveloping a hydraulic pressure, flexible fluid transmission meansbetween said units, said power unit comprising a base portion having aplate secured thereto, a chainconnected to said plate and looped about ametal member, a plunger in said power unit, a plate secured to theprojecting end of said plunger, and a chain connected to said plate andlooped about a second metal member,

said plunger moving outwardly of said base portion upon transmission ofpressure to said power unit for producing a tension stress upon said,

chains between said-metal members.

10. In a pulling mechanism of the class described, a power applying unitcomprising a ram cylinder and an axially movable plunger, a chainpullplate carried by said cylinder, a chain-pull plate carried by saidplunger, means for securing chains to said plates, said chains beinglooped about a pair of spaced metal members, and means ata point remotefrom said unit for developing a hydraulic pressure including means fortransmitting said pressure to said power unit independently of stressesincident to development of said pressure whereby said plunger is movedoutwardly of said ram cylinder to produce a tension stress on saidchains between said members.

11. In a pulling mechanism of the class described, a ram unit comprising;a ram cylinder and an axially movable plunger therein, chain-' pullplates carried by' said cylinder and said 12. The method of. pulling twospaced members toward each other which comprises connecting chains toeach of said members, movably supporting the end of each chain with theadjacent portion of the other chain in overlapped position between saidmembers, and spreadingthe supported ends of said chains apartto exert astraight line pulling stress between saidspaced members to reduce thespacing between said members. v

13; Themethod of producing a pulling stress between two spaced memberswhich comprises securing tension means to said members, extending theends of said means into the space between said members in overlappingrelation, connecting the extending portions of said means to oppositeends of a power unit so that the tension means from one of said spacedmembers extends alongside said power unit and is connected tothe far endthereof, the other tension means extending from the other spaced memberalongside said power unit and being connected with the opposite end ofthe latter, and hydraulically expanding said unit to separate said endsand pull the portions of said tension means engaging said members towardeach other.

14. The method of producing a pulling stress between two spaced memberswhich comprises wrapping chains about said members, extending the endsof said chains into the space between said members, connecting theextending portions mote from'said members, transmitting said pressure tosaid unit independently of stresses developed at said remote point, andhydraulically expanding said. unit by said pressure to pull the portionsof said chains engaging said members toward each-,other.

15. In combination, a power unit comprising a ram cylinder and anaxially movable ram plunger therein, a plate secured to the base of saidcylinder, a pair of rod members carried by said plate and extendingalong opposite sides of said cylinder past the opposite end thereof, asecond plate secured across the extending ends of said rods, a thirdplate slidably mounted on said rods intermediate the cylinder and theends of said rods and secured. to said plunger, chain means wrappedaround a metal member and connected to said second plate, chain meanswrapped around a second metal member and secured to said third plate,said power unit being placed between said' metal members, and means forhydraulically moving said plunger outwardly of said 16. In combination,a power unit comprising a ram cylinder and an axially movableramplungertherein, a plate secured to the base of said cyl-' inder, apair of'rod members carried by said plate and extending along oppositesides of said cylinder past the opposite end thereof, a second platesecured across the extending ends of said rods, a; third plate slidablymounted on said rods intermediate the cylinder and the ends of said rodsand secured to said plunger, chain means wrapped around a metal memberand adjustably connected to said second plate, chain means wrappedaround a second metal member and adjustably secured to said third plate,said power unit being placed between said metal members, means remotefrom said unit for developing a hy-' chains carried by each of said pullplates and guided for movement through the opposite pull plate, andmeans at theextending ends of said chains for securing them to metalmembers spaced away from opposite ends of said unit.

18. A chain pull plate comprising a central portion having aninternally. threaded recess therein, a pair of oppositely extending armportions having guide openings therethrough, and

7 an intermediate axially projecting boss portion members, applying aseparating force to the opposite said recess having an opening extendingtherethrough normal to the axes of said guide openings and intermediatesaid arm portions. v

19. The method of pulling two spaced members toward each other'whichcomprises connecting flexible tension members toeach of said spacedmembers, overlapping the ends'of said flexible spaced apart ends of theoverlapped portions of said flexible members in alignment with thelatter-so'as to force the overlapped ends of said tension: members apartto exert a pulling stress be tween said spaced members, and supportingthe force applying means on said flexible tension members at pointsspaced around the ends- 20. In a pulling mechanism of the classdescribed, a ram unit having an axially movable plunger, a platemembersecured to the base of said unit, a second plate member carried-bysaid movable plunger, there being openings formed in, said second platemember, tension transmitting means carried by said second plate memberand extending alongside said ram unit and adjacent said first platemember, and tension means connected with said first plate member andextending alongside said unit in a direction opposite to said firstmentioned tension means outwardly of the unit through the openings insaid second mentioned plate member.

21. In a mechanism of the class described, a power unit, pull plates atopposite ends of said unit, flexible tension members having their outerend portions connected with spacedmetal members and having their innerends extending in overlapped'relation and secured, respectively, to

the furthermost pull plate, and means for applying hydraulic pressure tosaid unit for moving said plates away from each other to produce atension stress upon said flexible members between said spaced metalmembers for pulling the latter toward each other.

22. A pull mechanism for producing a tension stress between two spacedmemberscomprising a first device for developing a hydraulic pressuredirectly under thecontrol of the operator; 9. second device mechanicallydisassociated from said first device-and operable in any desired angularposition for producing a straight line force, means coupling saidmembers in overlapped relation to opposite ends of said second device;

and a third device comprising a flexiblepressure transmitting memberconnecting said other two I devices and transmitting pressure from saidfirst device to said second device independently of stresses produced bydevelopment of sure at said'flrst device.

23. I'he-method of pulling two spaced members toward each other whichcomprises engaging each of said members by a flexible tension member,overlapping the tree portion of said tension members','connecting saidoverlapped portion tothe opposite ends of expansible means,- supportingsaid means in position between said a spaced members in the line ofstresstherebetween on portions of said tension members inter- I mediatesaid spacing members and the points of connection of said tensionmembers to said means while PI'OVidiIlEfl-GB movement of said Hiintermediate portions of said tension members with respect to saidmeans, and expanding said means to pull the engaged portions of saidtension members toward each other.

' 24.'In' an assembly for pulling two spaced members toward each otherincluding a ram unit comprising a cylinder and an axially extensiblepiston carried thereby and having pull plates secured to the'base ofsaid cylinder and to the outer end of said piston, the method ofproducing a tension stress between said members which comprises engagingeach or said members by flexible tension means, connecting each tensionmeans to opposite sides of the pull 'plate disposed remote from themember with whicli'the tension means is engaged with the in-- termediateportions of said tension means in overlapped position along the sides ofsaid unit, guiding said intermediate portions of said tension means formovement relative to said unit' on the ends of said unit adjacent themember with which each of said tension means is en-- gaged to therebysupport said unit on said ten*- sion means in line with the direction ofstress.

